An image reading apparatus, such as a scanner, typically captures an image of a document while conveying the document using an imaging device, such as a line sensor, where imaging elements are one-dimensionally arrayed. If a dirt substance, such as paper dust, other fine particles, or glue, adheres to a glass surface of the imaging device, noise line extending in a document conveyance direction is generated in an image captured a document. Thus, an image reading apparatus and an image processing system having an image reading apparatus need to appropriately detect a dirt substance from an image.
There has been disclosed an image reading apparatus that includes a conveyance device that conveys a document along a conveyance path, a CCD unit that reads a document at the reading position in the conveyance path, and a control module that controls to read a shadow of a document being conveyed along the conveyance path. This image reading apparatus determines a dirt substance at a reading position based on the shadow of a document read by the CCD unit (refer to Japanese Unexamined Patent Publication (Kokai) No. 2010-74530).